Low-density parity check (LDPC) codes are used in transmitting signals over noisy transmission channels. LDPC codes and other error correction codes decrease the probability that information transmitted over the noisy channel is lost. Repeat Accumulate and Irregular Repeat Accumulate (IRA) codes can be viewed either as structured LDPC codes or as concatenated codes. IRA codes perform as well as the best unstructured LDPC codes, reaching rates approaching capacity on the additive white Gaussian noise (AWGN) channel. Modern turbo-like codes (TLCs), including concatenated convolutional codes and LDPC codes, have been shown to approach the Shannon limit on the AWGN channel. Systematic with Serially Concatenated Parity (S-SCP) codes are a class of codes, where a single decoder can provide performance close to theoretical limits over a wide range of block sizes, code rates, and desired frame error rates.